Abstract:
The interactions between biological activity and physico-chemical characteristics of landfast first year sea ice were investigated in McMurdo Sound as a multiparametric analysis of the physico-chemical properties of the ice. The first phase occurred in early spring (when the photosynthetic activity restarts - October 1999), the second at the beginning of summer (November 2001) and the last phase ... at the end of a full season of photosynthetic activity (January 2003). Sampling was conducted along a transect reflecting decreasing proportion of platelet ice from a south to north orientation. Ice cores were collected from several locations along the transect. Four locations were sampled in the first phase, 9 locations in the second phase and 6 locations in the last phase, with between 4 and 8 cores taken from each location. The cores from the first and last phases were analysed for temperature profiles (in situ), salinity profiles, texture and fabric, stable isotopes, minor elements (e.g. Fe, Mn, etc), total gas content and gas composition. The second phase sampling was unusual due to the grounding of the iceberg B15-A impeding the removal of the sea ice cover by ocean currents. An additional five sites were chosen further north to be able to sample both thick and thin first year ice. At each site, a set of 8 cores was sampled and analysed for total iron content, iron speciation and isotopes, salinity, δ18O and δD of the ice, total gas content, gas composition in O2, CO2, N2 CH4 and DMS, DMSP, algae speciation, Chl-a and bacterial counts. Ice temperature was measured at a 5-10cm resolution. During the second and last phase, one core from each location was sectioned on site at selected depths, for in situ melting and biological preservation of the samples for phytoplankton studies and bacterial counts for comparison with frozen cores. Water samples were collected from the ice water interface for iron determination, algae speciation, bacterial counts and gas measurements. Rock samples and sediment samples from the bottom were also collected for iron measurements where available. Samples of algae were cultured to for experimental procedures addressing environmental stresses (light, temperature and trace elements) on algal metabolism.